Cutting force variability as a consequence of exchangeable cleavage fracture and compressive breakdown of wood tissue
Cutting force variability as a consequence of exchangeable cleavage fracture and compressive breakdown of wood tissue
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木材组织的可交换解理断裂和压缩破坏导致切削力变化
DOI：
10.1007/s00226-011-0457-4
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发表时间：
2012
影响因子：
3.4
通讯作者：
B. Bučar
中科院分区：
文献类型：
--
作者：
M. Merhar;B. Bučar
本文研究了山毛榉（Fagussilvatica）木材在90° ~ 0 °方向正交斜切时I型切屑的扩展或断裂条件。正交木材切削所需的力是明显可变的，这是材料分解方式可互换的结果。切屑形成过程是不连续的，因为在切削刀具前面的材料的中断分裂。以31°和42°的前角切割10 mm厚的试样，切屑厚度范围为0.1至0.3 mm。切屑段长度随着切屑厚度的增加而增加。不同长度和厚度的芯片建模使用有限元方法。对于每种情况，在芯片和裂纹尖端的应力强度因子的弯曲或压缩应力进行了计算。当裂纹尖端的应力强度因子KI等于临界应力强度因子KIC，且切屑中的弯曲或压缩应力σ小于强度σu时，考虑裂纹扩展的条件，可以计算切屑的段长。计算值和测量值之间的良好协议进行了观察。切屑段长度可以随着弯曲强度和临界应力强度因子的微小变化而显著变化。这种大的灵敏度也证实了所测量的芯片段长度的波动高达400%。
In the present study, the conditions of chip propagation or fracture in orthogonal oblique cutting of beech wood (Fagus silvatica) in the 90°–0° direction for a type-I chip has been investigated. The force required for orthogonal wood cutting is pronouncedly variable, which is the consequence of exchangeable different ways of material breakdown. The chip formation process is discontinuous because of interrupted splitting of the material in front of the cutting tool. A 10-mm-thick specimen was cut at a rake angle of 31° and 42° with chip thicknesses ranging from 0.1 to 0.3 mm. The chip segment length increased with the chip thickness. A chip of varying length and thickness was modelled using the finite element method. For each case, the bending or compressive stress in the chip and the stress intensity factor at the crack tip was calculated. The segment length of the chip can be calculated by taking into account the condition that a crack propagates when the stress intensity factorKIat the crack tip equals the critical stress intensity factorKIC, and the bending or compressive stressσxin the chip is smaller than the strengthσu. Good agreement between the calculated and the measured values was observed. The chip segment length can change considerably already with small changes in the bending strength and critical stress intensity factor. This large sensitivity is also confirmed by the fluctuation of the measured chip segment lengths by as much as 400%.